PCA Forums

This is puzzling to me. I bought 2 used Dell laptops cheap because when powered on, the Dell logo would briefly be displayed and then the laptop would shot off.

After I disassemble the laptop, one of the checks I do is the CMOS battery using a Fluke DMM. The CMOS battery shows 2.9 volts. So I continue to trouble shoot, but this time I decided to take the CMOS battery out. I used this battery tester https://www.ztsinc.com/mbt1.html and the CMOS battery is dead. Not even 1 bar on the tester. So why would the CMOS battery indicate voltage on the Fluke DMM?

Anyway, I replaced them and the laptop now works fine. I know my Fluke meter works fine, because I checked it with another Fluke meter with the same results. Is this because there is still some voltage in the battery, and if I left it on the DMM, would the voltage gradually drop?

I've seen dead CMOS batteries witn even higher voltages. Voltage alone means little. You want to put rhe battery under load, and then check the voltage, which is what a tester does.

If you don't have a tester, then I would throw out any battery that comes up less than 3.1 volts on a digital multimeter. A brand new CR2032 will generally read around 3.2 volts without any load on it.

I still have the battery, and what I did was to test it again with the Fluke DMM while I watch the readings. They continue to decrease while I was testing it. So I'll have to remember this next time when checking them. If they start to drop in voltage, they probably need to be replaced.